1. Field of the Invention
The present invention relates to a receiving apparatus and method employing a multi-carrier transmission method utilizing real coefficient wavelet filter banks (Digital Wavelet Multi-Carrier transmission method, which is hereinafter called “DWMC transmission method”).
2. Description of the Related Art
The transmission method involving digital modulation and demodulation processes utilizing real coefficient wavelet filter banks is a type of multi-carrier modulation method in which a plurality of digital modulated waves are synthesized from real coefficient filter banks to generate a transmission signal. In the method, PAM (Pulse Amplitude Modulation) is used as a method for modulating each carrier.
A data transmission method according to the DWMC transmission method will be described with reference to FIGS. 26 to 29.
As shown in FIG. 26, each subcarrier has an impulse response, and impulse responses of each of the plurality of subcarriers are transmitted in an overlapping relationship with each other. As shown in FIG. 27, each transmission symbol is formed by a time waveform that is a combination of impulse responses of a plurality of subcarriers.
The spectrum diagram shown in FIG. 28 illustrates an example of a transmitted spectrum according to the DWMC transmission method. A transmission frame (shown in FIG. 29) is formed by several tens to several hundreds of transmission symbols according to the DWMC transmission method. This transmission frame includes a symbol for a transmission of an information data, a symbol for a frame synchronization, and a symbol for an equalization.
Since a clock of a receiver is not exactly consistent with a clock of a transmitter in multi-carrier communications, receiving quality of the receiver may degrade because a bit error rate may rise in the receiver. The insertion of a pilot-carrier in carriers has been considered as a method to compensate for the clock-inconsistency. However, the usability of the frequency will degrade in this case. Furthermore, a method to compensate for the clock-inconsistency between the transmitter and the receiver may not have been established in the DWMC transmission method.